1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Evaluate the change in redshift over 10 years

  1. Dec 11, 2013 #1
    1. The problem statement, all variables and given/known data

    I am given a model where for an accelerating universe the redshift changes according to the following equations (given in part b). For this model and assuming that H0=70km/s/Mpc, evaluate the change in redshift over 10 years, for a source at z=1 and the change in recession velocity

    2. Relevant equations
    rate of change is [itex]\frac{dz}{dt}[/itex]=H0(1+z)-H(z) where H(z) is the Hubble parameter
    In this case I am considering a κ=0 universe with no cosmological constant, so H(z)=H0(1+z)3/2


    3. The attempt at a solution
    I know that the long way would be to take the integral of the [itex]\frac{dz}{dt}[/itex] formula from z=1 to z' over the entire time period. What I am wondering is, because of how minute the change would probably be is it acceptable to approximate this as:
    Δz≈t1H0(1+z-((1+z)3/2)) where t1=10 years?
     
    Last edited: Dec 11, 2013
  2. jcsd
  3. Dec 12, 2013 #2
    I am asking because when I calculate this I get a negative number for the change in z. Wouldn't this be a blueshift?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted